SS7 ANSI-41 TO SIP BASED CALL SIGNALING CONVERSION GATEWAY FOR WIRELESS VoIP E911

ABSTRACT

An SS7-based call protocol conversion gateway that translates between circuit-switched SS7 protocols and session initiation protocol (SIP) oriented protocol, allowing an E911 call initiated over a switched network to be routed by a VoIP network. The SS7-based call protocol conversion gateway provides a PSAP with MSAG quality (street address) information about a VoIP dual mode phone user without the need for a wireless carrier to invest in building out an entire VoIP core. Thus, wireless carriers may continue signaling the way they are today, i.e., using the J-STD-036 standard for CDMA and GSM in North America, yet see benefits of a VoIP network core, i.e., provision of MSAG quality location data to a PSAP.

The present application claims priority from U.S. Provisional PatentApplication No. 60/788,713, filed Apr. 4, 2006, entitled “SS7 ANSI-41 TOSIP BASED CALL SIGNALING CONVERSION GATEWAY FOR WIRELESS VoIP E911”, toMitchell, the entirety of which is expressly incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to E9-1-1 emergency phone calls. Moreparticularly, it relates to handling emergency E9-1-1 calls using VoiceOver Internet Protocol (VoIP).

2. Background of the Related Art

Voice Over Internet Protocol (VoIP) is a technology that has beendeveloped as an alternative packet-based telephony technology to theconventional switched telephony service (e.g. PSTN). VoIP takesadvantage of high speed Internet data networks, and is able to providelow cost telephony services to end users. VoIP technology emulates aphone call, but instead of using a circuit based switched system such asthe telephone network, utilizes packetized data transmission techniquesmost notably implemented in the Internet.

VoIP phone calls are routed to a VoIP voice gateway, from which they arepassed on to their destination VoIP device. Conventional VoIP voicegateways (i.e., soft switches) are typically located in only a fewplaces across the country. A soft switch is a programmable networkswitch that can process the signaling for all types of packet protocols.Also known as a ‘media gateway controller,’ ‘call agent,’ or ‘callserver,’ such devices are used by carriers that support convergedcommunications services by integrating signaling system No. 7 (SS7) typeswitched telephone signaling with packet networks. Softswitches cansupport, e.g., IP, DSL, ATM and frame relay.

Because VoIP is Internet Protocol (IP) based, call related informationsuch as CallerID type services may not be available or accurate. Alocation of a given VoIP device may be statically provisioned to be at agiven geographic location, or queried from a home location register(HLR) in a mobile system.

911 is a phone number widely recognized as an emergency phone numberthat is routed to emergency dispatch personnel and used to determine alocation of a caller. Enhanced 911 (E911) is defined by the transmissionof callback number and location information to the relevant publicsafety answering point (PSAP). A PSAP is the endpoint of an emergencyservices call. PSAPs are responsible for answering emergency servicescalls. E911 may be implemented for landline and/or mobile devices. SomePublic Safety Access Points (PSAPs) are not enhanced, and thus do notreceive the callback or location information from any phone, landline ormobile.

The problem is not necessarily solved with the use of a centralizedemergency call center. In such case, when a VoIP customer places anemergency call such as an E911 call, the call may be routed to anemergency call center that is very far away, and in some instanceshalf-way across the world to reach the centralized emergency callcenter. The VoIP E911 call must then be transferred to the relevant 911center (public safety access point (PSAP)). However, this transfer musttake place over the Public Switched Telephone Network (PSTN) becausesuch transfer cannot conventionally be gained to the PSAP's existingEnhanced 911 (E911) dedicated network where location and callback numberof the originating 911 caller are provided. Moreover, note that even thecall related information (e.g., CallerID) provided with the call wouldrelate to the identity and location of the centralized call center—notto the callback number and certainly not the location of the customeroriginally dialing 911.

FIG. 7A shows conventional relevant systems in an emergency 911 callmade via a wireless caller in a GSM network.

In particular, as shown in FIG. 7A, a wireless GSM caller 190 dials 911.The 911 call is serviced by a cell site of a service provider, whichincludes a given mobile servicing center (MSC) 402. The MSC 402 performsa query of a PSAP Automatic Location Identification (ALI) database 406via a gateway mobile location centre (GMLC) 432 to determine a unique10-digit phone number of the proper local PSAP physically responsiblefor the location of the 911 caller 190.

FIG. 7B shows conventional relevant systems in an emergency 911 callmade via a wireless caller in a CDMA or TDMA network.

In particular, as shown in FIG. 7B, a wireless CDMA or TDMA caller 190 bdials 911. The 911 call is serviced by a cell site of a serviceprovider, which includes a given mobile servicing center (MSC) 402. TheMSC 402 performs a query of a PSAP Automatic Location Identification(ALI) database 406 via a mobile positioning center (MPC) 707 todetermine a unique 10-digit phone number of the proper local PSAPphysically responsible for the location of the 911 caller 190 b.

As technology progresses, dual mode wireless phones have emerged. A dualmode wireless phone is one that operates using CDMA or GSM technologywhen out on the open road, but which switches to a local area networksuch as a Wireless Fidelity (WiFi) network when within range at home orin the office. For instance, a wireless phone may join a WiFi networkcreated in a home or office used by a wireless computer network, whenwithin range of that WiFi network, to gain access to the Internet andthus communicate using voice over Internet Protocol (VoIP). Thus, dualmode phones operate as an ordinary cell phone as a mobile user traversesa cell network (e.g., a CDMA network), until you get home or to youroffice containing a WiFi network, at which time the cell phone drops useof the CDMA network and instead switches over to use of the WiFinetwork.

When a wireless phone is mobile and away from home or the office,latitude/longitude location information is pretty much the best that canbe provided. However, when within a home or office on a WiFi network, itis preferable that more accurate location information such as MSAGformat location information including street address be provided insteadof merely lat/lon type location information.

Unfortunately, provision of MSAG format location information along witha WiFi wireless call presents significant expense to a wireless carrier.Instead, without change to the wireless carrier's network, lat/lonlocation information is the best that can be provided in all cases, evenwhen the wireless dual mode phone is communicating over the Internetusing a WiFi network.

FIG. 8 shows one conventional solution to delivery of location data inwireless E911 format, but providing only latitude/longitude (lat/lon)location information.

In particular, as shown in FIG. 8, a wireless caller 190 using a dualmode phone dials 911.

A user agent 180 provides service to the wireless VoIP device 190 sothat the dual mode phone is provided with wireless Internet access.(“User agent” is a common name for a device that makes a VoIP call,e.g., a SIP phone, Skype™ on a Personal Computer, etc.)

The call then progresses over the Internet (Voice Over Internet Protocol(VoIP)) via a wireless fidelity (WiFi) access point 170. A WiFi accesspoint 170 is, e.g., a wireless local area network hub in a house oroffice. The WiFi access point 170 provides Internet access to thewireless dual mode phone 190 typically via a wired connection to theInternet. (While described with respect to WiFi, the invention asdescribed below relates equally to later embodiments of local areanetwork hot spots (e.g., WiMAX, etc.).

A wireless VoIP base station controller 160 communicates with the WiFiaccess point 170 to provide circuit switched, time-division multiplexing(TDM) access to the VoIP call.

The user agent 180, WiFi access point 170 and a Wireless VoIP basestation controller 160 use TCP/IP transport and session initiationprotocol (SIP) protocols.

From the wireless VoIP base station controller 160, the VoIP E911 callis passed to a mobile switching center (MSC) 800. If part of a CDMAnetwork, the MSC 800 passes an Origination Request (ORREQ) message(IS-41) to a 3^(rd) Generation Partnership (3GPP2) mobile positioningcenter (MPC) 802 per the 3GPP2 joint standard #36 (J-STD-036). The ORREQstarts the process where location is ultimately obtained from a PositionDetermination Entity (PDE). The PDE consumes, or uses, the locationinformation itself.

If part of a GSM network, the MSC 800 passes a subscriber locationreport (SLR) request to a Gateway Mobile Location Center (GMLC) 802. AnSLR is a push of location. Thus, location is actually obtained beforethe message is sent. In such a GSM network, the MSC 800 actually getsthe location back from the network element (SMLC) on the time divisionmultiplex (TDM) side. The MSC 800 then provides the location to the GMLC802.

The VoIP E911 call is then directed to a selective router 140 servingthe designated public safety access point (PSAP)/911 network 195 for thedetermined lat/lon location.

FIG. 9 shows a conventional delivery of location data in MSAG format forVoIP calls for processing E911 calls using the NENA approved i2 callflow.

In particular, as shown in FIG. 9, a dual mode phone user 190 makes a911 call over their WiFi network as otherwise described in FIG. 8. Forinstance, the VoIP E911 call is serviced by a user agent 180, a WiFiaccess point 170, and a wireless VoIP base station controller 160, asotherwise shown and described with respect to FIG. 8. However, in theembodiment of FIG. 9, the wireless carrier is a voice service providernetwork 900, enjoying the benefits of a VoIP network.

The voice service provider network 900 passes a SIP invite message to aVoIP positioning center 904. The SIP invite is used to get locationinformation from the VPC 904. In this scenario, location is determinedby the VPC 904, and the VPC 904 is used to make decisions based on thatlocation. In particular, the VPC 904 sends signaling to the VSP 900 sothat it can get the call to the right PSAP 195, but the locationinformation itself is not sent back to the VSP 900. Rather, justsignaling codes necessary to route the VoIP E911 call to the properselective router 140 and PSAP 195 (via an emergency services gateway902) are sent from the VPC 904 to the VSP 900. (An emergency servicesgateway (ESGW) is typically a function inside a standard media gateway.A media gateway is typically TCP/IP on one side, and TDM trunks on theother side.)

Location information itself in the embodiment of FIG. 9 is maintained ina subscriber line database (SLDB), created from an out-of-bandtransaction. This means that the dual-mode phone user 190 presets theirMSAG format location into the SLDB, e.g., by logging into a suitableSLDB portal during registration of their dual-mode phone, and enterstheir location (e.g., relevant street address). The PSAP 195 accessesthis MSAG quality location information using a automatic locationidentificatier (ALI) query to the VPC 904, which in turn pulls locationdata from the SLDB, formats it, and provides it back to the PSAP 195.

Trials have been conducted in which a local exchange carrier (LEC) haspermitted access to a selective router for the E911 network via thePSTN. In this trial, the LEC designated a specific 10-digit telephonenumber. A caller has their emergency call transferred to this 10-digittelephone number, which is then call-forwarded within the central officeto the selective router, which then forwards the call to the correctPSAP based upon the digits dialed. However, this solution suffers thesame significant drawbacks as that shown in FIG. 7, i.e., that callbacknumber and location are not provided to the responsible PSAP.

Thus while carriers continue to accommodate and indeed fosterdevelopment of a nationwide VoIP telephone network, difficultiesnevertheless abound, particularly with respect to provision of locationof a VoIP caller to an emergency response center. As a result, wirelesscarriers wishing to offer dual-mode phones to customers must makesignificant technology investments and infrastructure upgrades to handleVoIP calls. (Dual-mode phones are capable of initiating mobile E9-1-1calls using, e.g., Global System for Mobile Communications (GSM) or codedivision, multiple access (CDMA), or even wireless fidelity (WiFi)). Thedesire is to handle use of such technologies in a VoIP communicationsnetwork. However, the reality is that many wireless carriers continue toutilize switched technology equipment at least at the front end incommunication with a VoIP caller. If an E911 call is placed, it islikely handled in the wireless carrier's network from a circuit switchedinterface. The present inventors realize that this causes a delay in theintroduction of VoIP technology, and reduced competition from othercarriers. Moreover, full compliance with national requirements may notbe possible, e.g., the need to provide location and callbackinformation.

There is the need for a simple and effective solution to providing easyand full access to the Enhanced 911 network of an emergency servicesprovider (e.g., PSAP) from wireless VoIP users of a carrier utilizing aswitched network.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, a callprotocol conversion gateway comprises a module adapted to receivesignaling system number 7 (SS7)-based call signaling. A module isadapted to convert the SS7 ISUP based call signaling into sessioninitiation protocol (SIP)-based call signaling, and a module is adaptedto pass the SIP call signaling to a voice over Internet (VoIP)positioning center.

A method of converting a VoIP call, passed over a switched telephonenetwork, into a VoIP call for presentation to a public safety accesspoint (PSAP) in accordance with yet another aspect of the presentinvention comprises receiving a voice over Internet protocol (VoIP) callfrom a VoIP phone via a local area network. The VoIP call is routedusing signaling system number 7 (SS7) ISUP based call signaling. The SS7ISUP based call signaling is converted into session initiation protocol(SIP) call signaling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing relevant software elements includingan SS7 based ANSI-41 J-STD-036 to SIP protocol conversion gateway usedto handle placement of an E911 call from a VoIP user through a wirelesscarrier including switched network components, in accordance with theprinciples of the present invention.

FIG. 2 is a call flow diagram showing relevant call flow with respect tothe use of an SS7 based ANSI-41 J-STD-036 to SIP protocol conversiongateway, in accordance with the embodiment shown in FIG. 1.

FIG. 3 is a block diagram showing relevant software elements includingan SS7 based MAP-Lg+ to SIP protocol conversion gateway used to handleplacement of an E911 call from a VoIP user through a wireless carrierincluding switched network components, in accordance with the principlesof the present invention.

FIG. 4 is a call flow diagram showing relevant call flow with respect tothe use of an SS7 based MAP-Lg+ to SIP protocol conversion gateway, inaccordance with the embodiment shown in FIG. 3.

FIG. 5 is a block diagram showing relevant software elements includingan SS7 based ISUP to SIP protocol conversion gateway used to handleplacement of an E911 call from a VoIP user through a wireless carrierincluding switched network components, in accordance with the principlesof the present invention.

FIG. 6 is a call flow diagram showing relevant call flow with respect tothe use of an SS7 based ISUP to SIP protocol conversion gateway, inaccordance with the embodiment shown in FIG. 5.

FIG. 7A shows conventional relevant systems in an emergency 911 callmade via a wireless caller in a GSM network.

FIG. 7B shows conventional relevant systems in an emergency 911 callmade via a wireless caller in a CDMA or TDMA network.

FIG. 8 shows one conventional solution to delivery of location data inwireless E911 format, but providing only latitude/longitude (lat/lon)location information.

FIG. 9 shows a conventional delivery of location data in MSAG format forVoIP calls for processing E911 calls using the NENA approved i2 callflow.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention provides a signaling system number 7 (SS7) gatewaydevice that translates between circuit-switched SS7 protocols andsession initiation protocol (SIP) oriented protocol, allowing an E911call initiated over a switched network to be routed by a VoIP network.

Use of an SS7 based gateway in accordance with the principles of thepresent invention, as opposed to the ORREQ technique shown in FIG. 8, orthe SIP Invite technique shown in FIG. 9, is that it provides a PSAPwith MSAG quality data without the need for carrier's to invest inbuilding out a VoIP core. The SS7 gateway approach forms a marriage ofthe best features of the embodiments of FIGS. 8 and 9. This saveswireless carriers significant amounts of cash because they don't need toswitch to a VoIP core (as in FIG. 9) to have the capability to provideMSAG quality location information over a TDM network (such as the oneshown in FIG. 8). This allows carriers to keep their existing networks,while at the same time adding MSAG location capabilities for WiFi users,all at minimal infrastructure cost.

The consumer benefits as well, as use of an SS7 gateway in a TDM networkprovides emergency services with a high quality MSAG type locationrather than just a lat/long quality location, when in their time ofneed.

Using todays systems, most wireless carriers provide lat/lon qualityinformation for all WiFi callers. While lat/lon information (e.g., celltower location, etc.) is somewhat accurate, it does not give emergencyservices personnel total comfort in their locating the caller in atimely fashion. However, using an SS7 based gateway inserted into a VoIPplatform including a voice positioning center (VPC), users can use adual mode phone, dial 911, and MSAG quality location information can beprovided to the designated PSAP, all without significant investment in aVoIP core by the wireless carrier. The home or office address (MSAGquality location information) can be given because it's based on theVoIP network.

Thus, wireless carriers may continue signaling the way they are today,i.e., using the J-STD-036 standard for CDMA and GSM in North America,but see benefits of a VoIP network core, i.e., provision of MSAG qualitylocation data to a PSAP.

In one aspect of the invention, SS7 based J-STD-036/TransactionCapabilities Application Part (TCAP) signaling is translated to SIP forpurposes of E911 call routing.

FIG. 1 is a block diagram showing relevant software elements includingan SS7 based ANSI-41 J-STD-036 to SIP protocol conversion gateway usedto handle placement of an E911 call from a VoIP user through a wirelesscarrier including switched network components, in accordance with theprinciples of the present invention.

In particular, as shown in FIG. 1, a wireless VoIP user 190 places a 911call, which is serviced by a user agent 180. The user agent 180 gainsaccess to the wired Internet via a WiFi access point 170, and access tothe wireless carrier's network via a wireless VoIP base stationcontroller 160.

From the wireless VoIP base station controller 160, the VoIP 911 callover a WiFi network is routed to the wireless carrier's Mobile SwitchingCenter (MSC) 150. Ultimately, the 911 call is routed to an appropriateselective router 140, and then to the proper PSAP E911 network 195.

Importantly, in accordance with the principles of the present invention,911 calls from the wireless MSC 150 are processed by an SS7 to SIPgateway 100 that accepts and sends SS7 TCAP [Transaction CapabilityApplication Part]/J-STD-036 based signaling, but gateways the callsignaling to session initiation protocol (SIP) signaling. Thus, the SS7to SIP gateway 100 communicates with the MSC 150 to translate fromJ-STD-036 TCAP to SIP, i.e., between wireless technologies and VoIPlocation technologies.

Preferably the SIP signaling is compliant to a relevant standard, butthere is currently no existing standardized SS7 interfaces allowed bythe current standards for VoIP E911, i.e., National Emergency NumberAssociation (NENA) i1/i2 standards for a voice over IP (VoIP)positioning center (VPC).

The SS7 to SIP gateway 100 translates call data received from the MSC150 (e.g., calling party number) into relevant SIP INVITE parameters.The call data is then passed to a voice over Internet protocol (VoIP)positioning center (VPC) 120 as a VoIP call.

The VPC 120 is an application that determines the appropriate PSAP,based on the location of the 911 caller 190, returns associated routinginstructions to the VoIP network, and provides the callback number tothe PSAP 195 through an automatic location identifier (ALI). (An ALI isa database that relates a specific telephone number to an address. Thisdatabase accepts a PSAP query with a telephone number and responds withan address. In the case of an ESQK, the ALI database steers (redirects)the query to the appropriate VoIP positioning center and steers theresponse back to the querying PSAP).

The SIP INVITE command from the SS7 to SIP gateway 100 preferablyincludes the following parameters:

-   -   a) The “from” field        -   =the dialed digits from the VoIP caller 190            -   (NPA-xxx-yyyy)    -   b) The “to” field        -   =911    -   c) The CBN field        -   =callback number of the VoIP caller 190

The SS7 to SIP gateway 100 receives routing instruction from the VoIPpositioning center (VPC) 120 and sends the routing key (e.g., emergencyservices query key (ESQK), a trunk select code (e.g., emergency servicesrouting number (ESRN)), and optionally an i1 public switched telephonenetwork (PSTN) number (e.g., last routing option (LRO)) back to the MSC150. (The ESRN is a 10-digit number that specifies the selective router140 to be used to route a call. The LRO is routing information sent bythe VPC 120 that provides a “last chance” destination for a call, forexample the contingency routing number (CRN) or a routing numberassociated with a national call center.)

The call then proceeds as it otherwise would for a wireless E911 call.

FIG. 2 is a call flow diagram showing relevant call flow with respect tothe use of an SS7 based ANSI-41 J-STD-036 to SIP protocol conversiongateway, in accordance with the embodiment shown in FIG. 1.

In particular, as shown in step 101 of FIG. 2, a caller 190 makes anE911 call while connected via a wireless IP based network.

The E911 call requires routing to a Public Safety Answering Point (PSAP)195 based upon the street address of the caller (e.g., MSAG qualitylocation data), which may be provisioned beforehand by the serviceprovider based on, e.g., a billing address, etc. Alternatively, the E911call can be routed to the correct PSAP 195 based on the absolutelocation of the caller, e.g., as determined by received data about theirwireless access node such as wireless fidelity (WiFi) access point 170.

The MSC 150 sends out signaling data related to the wireless E911 callusing the J-STD-036/TCAP protocol standard, including use of a TCAPmessage OriginationRequest (ORREQ). The TCAP OriginationRequest messageshould contain the calling party's number (CgPN) and called pary number(e.g., 911, etc.)

In step 102 of FIG. 2, the SS7 to SIP gateway 100 translates receivedJ-STD-036/TCAP parameters into session initiation protocol (IETF), i.e.,into SIP INVITE parameters.

In step 103 of FIG. 2, the VoIP positioning center (VPC) 120 assignsrouting based upon the location retrieved from the location informationservice/subscriber line database (LIS/SLDB) 130.

Preferably the SLDB is configured so that no modifications are requiredto the core conventional existing VoIP E9-1-1 network. The SLDB 130 isused to relate a Session Initiated Protocol (SIP) Universal ResourceIdentifier (URI) or a telephone number to a PSAP. In databases that usetables in lieu of GIS for routing determination, the address of the“subscriber” can be any valid street address within the jurisdiction ofthe PSAP.

In step 104 of FIG. 2, the SS7 to SIP gateway 100 receives routinginstruction from the VoIP positioning center (VPC) 120, including anemergency services query key (ESQK) and an emergency services routingnumber (ESRN), and translates these NENA i2 standard elements intowireless E911 elements, e.g., ESQK=ESRK; ESRN=Trunk select code; and,optionally an i1 PSTN number, e.g., (LRO)).

In step 105 of FIG. 2, the MSC 150 then egresses the call based upon theESRK and the trunk select code for use by the selective router 140. Theselected selective router 140 delivers the call to the assigned PSAP,e.g., PSAP 195, based upon the ESRK.

In another aspect of the invention, SS7 based TCAP/MAP/Lg+ signaling istranslated to SIP for purposes of E911 call routing.

FIG. 3 is a block diagram showing relevant software elements includingan SS7 based MAP-Lg+ to SIP protocol conversion gateway used to handleplacement of an E911 call from a VoIP user through a wireless carrierincluding switched network components, in accordance with the principlesof the present invention.

In particular, FIG. 3 shows calls from a wireless MSC processed by a SS7to SIP gateway 200 that accepts and sends SS7 TCAP (TransactionCapability Application Part)/MAP based signaling (Lg+ interface), butgateways the signaling to SIP protocol signaling. Again, ideally the SIPsignaling is compliant to a relevant standard for SIP signaling in aVoIP network, if existing and in place.

The 911 call from the wireless VoIP user 190 is routed to the wirelesscarrier's Mobile Switching Center (MSC) 150 via a user agent 180 for thewireless VoIP device, a WiFi access point 170, and a UMA networkcontroller UNC 220.

This aspect of the invention creates an SS7 based gateway 200 thattranslates from mobile application part; interface specification Lg+(MAP Lg+) to SIP. The SS7 based MAP-Lg+ to SIP gateway 200 is incommunication with the MSC 150, and serves as a translator betweenwireless technologies and VoIP location technologies.

The SS7 based MAP-Lg+ to SIP gateway 200 translates the call datareceived from the MSC 150 (e.g., calling party number) into SIP INVITEparameters, which are then passed to a VPC 120 as a voice over IP (VoIP)call.

The SS7 based MAP-Lg+ to SIP gateway 200 receives routing instructionfrom the VPC 120 and sends a routing key (e.g., an emergency servicesquery key (ESQK), trunk select code (e.g., emergency services routingnumber (ESRN), and (optionally) an i1 public switched telephone network(PSTN) number, e.g., last routing option (LRO) back to the MSC 150. The911 call then proceeds as it would otherwise for a wireless E911 call.

FIG. 4 is a call flow diagram showing relevant call flow with respect tothe use of an SS7 based MAP-Lg+ to SIP protocol conversion gateway 200,in accordance with the embodiment shown in FIG. 3.

in particular, as shown in step 201 of FIG. 4, a caller makes an E911call while connected via a wireless IP based network. The 911 callrequires routing to a public safety answering point (PSAP) based uponthe street address of the wireless VoIP caller 190 (which is provisionedbeforehand), or their absolute location (determined by received dataabout the wireless access node associated with the WiFi access point170.

The MSC 150 sends out signaling data related to the VoIP 911 call over aWiFi network using MAP/Lg+. Preferably the MAP message, i.e.,“SubscriberLocationReport (SLR)” contains the calling party number(CgPN) and called party number (i.e., 911 etc).

In step 202 of FIG. 4, the SS7 based MAP-Lg+ to SIP conversion gateway200 translates received MAP/Lg+ parameters into SIP INVITE parameters.

In step 203 of FIG. 4, the VPC 120 assigns routing based upon thelocation retrieved from the relevant location information server(LIS)/subscriber line database (SLDB).

In step 204 of FIG. 4, the SS7 based MAP-Lg+ to SIP conversion gateway200 receives routing instruction from the VPC 120 (e.g., an emergencyservices query key (ESQK) and an emergency services routing number(ESRN), and translates these NENA i2 standard elements into WirelessE9-1-1 elements. For instance, the ESQK is translated into an emergencyservices routing key (ESRK), the ESRN is translated into a trunk selectcode for use by the selective router 140, and optionally an i1 PSTNphone number, e.g., last routing option (LRO).

In step 205 of FIG. 4, the MSC 150 then egresses the 911 call based uponthe ESRK and the trunk select information to the relevant selectiverouter 140, which delivers the 911 call to the PSAP based upon the ESRK.

In yet another aspect of the invention, SS7 based ISUP signaling istranslated to SIP, e.g., for purposes of E911 call routing.

FIG. 5 is a block diagram showing relevant software elements includingan SS7 based ISUP to SIP protocol conversion gateway used to handleplacement of an E911 call from a VoIP user through a wireless carrierincluding switched network components, in accordance with the principlesof the present invention.

In particular, FIG. 5 shows calls handled by a wireless MSC 150 areprocessed by an SS7 based ISUP to SIP conversion gateway 300 thataccepts and sends SS7 ISUP based signaling, but gateways the signalingto SIP signaling. Preferably, the SIP signaling to which the SS7 basedISUP to SIP conversion gateway 300 converts is fully compliant to anyapplicable standard, if available.

The 911 call from the wireless VoIP user 190 is routed to the wirelesscarrier's Mobile Switching Center (MSC) 150 as shown. The SS7 based ISUPto SIP conversion gateway 300 then translates from integrated servicesuser part (ISUP) protocols into SIP protocol signaling.

The SS7 based ISUP to SIP conversion gateway 300 is in communicationwith the MSC 150, and serves as a translator between wireless and VoIPlocation technologies. The SS7 based ISUP to SIP conversion gateway 300translates call data received from the MSC 150 (e.g., calling partynumber) into appropriate SIP INVITE parameters, which are then passed tothe VPC 120 as a VoIP call.

The SS7 based ISUP to SIP conversion gateway 300 receives routinginstruction from the VPC 120 and sends the routing key (e.g., theemergency services query key (ESQK), trunk select code (e.g., emergencyservices routing number (ESRN), and (optionally) an i1 public switchedtelephone network (PSTN) phone number, e.g., last routing option (LRO)back to the MSC 150. The VoIP/WiFi 911 call then proceeds as it wouldfor a wireless E911 call.

FIG. 6 is a call flow diagram showing relevant call flow with respect tothe use of an SS7 based ISUP to SIP protocol conversion gateway 300, inaccordance with the embodiment shown in FIG. 5.

In particular, as shown in step 301 of FIG. 6, a caller makes an E911call while connected via a wireless IP based network (e.g., WiFi). Thecall requires routing to an appropriate public safety answering point(PSAP) based upon the street address of the dual-mode phone user 190(which is provisioned beforehand), or their absolute location (e.g.,determined by received data about the lat/lon of the WiFi wirelessaccess node 170.

The MSC 150 sends out signaling data related to the call using ISUP.Preferably, the IAM contains the calling party number (CgPN) and calledparty number (e.g., 911, 411, etc.)

In step 302 of FIG. 6, the SS7 based ISUP to SIP conversion gateway 300translates received ISUP IAM parameters into relevant SIP INVITEparameters.

In step 303 of FIG. 6, the VPC 120 assigns routing based upon thelocation retrieved from the location information server (LIS) orsubscriber line database (SLDB) 130.

In step 304 of FIG. 6, the SS7 based ISUP to SIP conversion gateway 300receives routing instruction from the VPC 120. Exemplary routinginstruction includes an emergency services query key (ESQK) and anemergency services routing number (ESRN), and translates these NENA i2standard elements into Wireless E9-1-1 elements. For instance, an ESQKis translated into an emergency services routing key (ESRK), an ESRN isconverted into a trunk select code for the relevant selective router140, and optionally an i1 PSTN number, e.g., last routing option (LRO).

In step 305 of FIG. 6, the MSC 150 then egresses the call to the properselective router 140 based upon the ESRK and trunk select information.The selective router 140 then delivers the E911 call to the proper PSAP195 based upon the ESRK information.

Accordingly, use of an SS7 to SIP conversion gateway in accordance withthe principles of the present invention provides for a low costarchitecture that has the ability to ease the transition from circuitswitched routing of wireless calls (including emergency calls such asE911) to Internet Protocol (IP) based routing of wireless calls (i.e.,voice over IP (VoIP)).

The invention has applicability to wireless carriers, and in particularto the use of dual-mode phones over local area wireless networks such asWiFi networks.

While the invention has been described with reference to the exemplaryembodiments thereof, those skilled in the art will be able to makevarious modifications to the described embodiments of the inventionwithout departing from the true spirit and scope of the invention.

1. A call protocol conversion gateway, comprising: a module adapted toreceive signaling system number 7 (SS7)-based call signaling; a moduleadapted to convert said SS7 ISUP based call signaling into sessioninitiation protocol (SIP)-based call signaling; and a module adapted topass said SIP call signaling to a voice over Internet (VoIP) positioningcenter.
 2. The call protocol conversion gateway according to claim 1,wherein: said SS7 call signaling relates to a wireless 911 call.
 3. Thecall protocol conversion gateway according to claim 2, wherein: said SS7call signaling relates to a VoIP wireless 911 call.
 4. The call protocolconversion gateway according to claim 1, wherein: said SS7 callsignaling relates to a VoIP wireless call made via a local area network.5. The call protocol conversion gateway according to claim 4, wherein:said local area network is a wireless fidelity (WiFi) network.
 6. Amethod of converting a VoIP call, passed over a switched telephonenetwork, into a VoIP call for presentation to a public safety accesspoint (PSAP), comprising: receiving a voice over Internet protocol(VoIP) call from a VoIP phone via a local area network; routing saidVoIP call using signaling system number 7 (SS7) ISUP based callsignaling; and converting said SS7 ISUP based call signaling intosession initiation protocol (SIP) call signaling.
 7. The method ofconverting a VoIP call, passed over a switched telephone network, into aVoIP call for presentation to a public safety access point (PSAP)according to claim 6, wherein: said local area network is a wirelessfidelity (WiFi) network.
 8. The method of converting a VoIP call, passedover a switched telephone network, into a VoIP call for presentation toa public safety access point (PSAP) according to claim 6, wherein: saidVoIP phone is a wireless phone.
 9. The method of converting a VoIP call,passed over a switched telephone network, into a VoIP call forpresentation to a public safety access point (PSAP) according to claim6, wherein: said VoIP phone is a dual mode phone.
 10. The method ofconverting a VoIP call, passed over a switched telephone network, into aVoIP call for presentation to a public safety access point (PSAP)according to claim 9, wherein: said dual mode phone has a first modeoperable in a cellular phone network, and a second mode operable in awireless fidelity (WiFi) network.
 11. The method of converting a VoIPcall, passed over a switched telephone network, into a VoIP call forpresentation to a public safety access point (PSAP) according to claim6, further comprising: assigning routing based upon a location retrievedfrom a location information service/subscriber line database (LIS/SLDB).12-20. (canceled)